In this audio, the key feature is the unique sound of a trombone, a brass instrument known for its distinct tones. The title "Trombone Slide Effect 3" indicates that the audio revolves around the third variant of a slide effect produced by this instrument. You can sense the stretching of the notes, akin to the physical stretching of the trombone's slide to achieve different pitches. The audio details a transformation, as the trombone's sound seamlessly shifts from one pitch to another, thereby creating a dynamic and engaging auditory experience.